Home Battery Thermal Insulation

Polyimide Foam for EV Battery & Energy Storage Thermal Protection

Certificate

UL 9540A

Typical Density

28-32kg/m3

Get a Quote

Lightweight Thermal Barriers for Lithium-Ion Battery Safety

JLON polyimide foam is a lightweight, flexible thermal barrier material developed for demanding lithium-ion battery applications.

It combines thermal insulation, flame resistance, compression recovery and electrical insulation in one material, making it particularly suitable for applications where a conventional rigid thermal barrier alone cannot accommodate battery cell expansion or assembly tolerances.

JLON PI foam can be used from cell level to battery pack level and energy storage cabinet level, including electric vehicle batteries and stationary battery energy storage systems (BESS).

Typical Applications

Cell-to-cell thermal barriers

Lithium-ion battery cell spacers

EV battery module insulation

Battery pack bottom, side and top liners

Module-to-enclosure thermal barriers

Battery thermal runaway propagation barriers

Energy storage battery pack insulation

BESS cabinet wall and door insulation

Adhesive-backed PI foam components

JLON Core Material

Need a material recommendation for your battery design?

Send us your cell type, available thickness, operating temperature and compression requirements.

Request Technical Support

Request a Sample

Why Battery Thermal Insulation Is Becoming More Important

Higher energy density and increasingly compact battery architectures place greater demands on passive thermal protection.

During a thermal runaway event, heat generated by one lithium-ion cell may transfer rapidly to neighboring cells. Thermal barrier materials are therefore used between cells, modules and surrounding structures to help reduce heat transfer and delay thermal propagation.

At the same time, lithium-ion cells expand and contract during repeated charge and discharge cycles.

This creates an additional engineering challenge:

A battery thermal barrier may need to insulate heat while also accommodating cell expansion and maintaining controlled compression.

Rigid materials such as mica can provide excellent high-temperature and electrical insulation, while aerogel provides extremely low thermal conductivity. However, these materials do not always provide the elasticity required for compression management.

This is where flexible polyimide foam provides a different combination of properties.

Four Functions in One Battery Thermal Barrier

1.Thermal Insulation

JLON PI foam helps reduce heat transfer between adjacent battery cells and other battery pack components.

Typical battery-grade test data show thermal conductivity of approximately:

0.04 W/(m·K)

This makes PI foam suitable for applications requiring a lightweight insulating layer combined with mechanical flexibility.

2.Thermal Runaway Propagation Protection

PI foam can be installed between battery cells or modules as part of a passive thermal protection system.

During abnormal heating or thermal runaway, the material helps reduce heat transfer to adjacent components and provides additional time before thermal energy reaches neighboring cells.

In a battery insulation sample test:

Hot-side temperature: 650°C

Maximum cold-side temperature: approximately 172°C

The actual thermal protection performance of a battery system depends on material thickness, density, compression ratio, cell chemistry, pack design and exposure conditions.

For this reason, thermal runaway performance should always be validated at the cell, module or pack level under the customer's actual design conditions.

3.Cell Expansion & Compression Management

Battery cells experience dimensional changes during charging, discharging and long-term cycling.

Flexible polyimide foam can deform under compression and help:

Absorb cell expansion

Compensate for assembly tolerances

Reduce gaps between components

Maintain contact pressure

Provide cushioning during vibration

Maintain thermal separation during repeated cycling

A tested battery-grade PI foam sample showed:

25% / 40% indentation ratio: 0.45

65% / 40% indentation ratio: 4.0

This compression behavior allows the material to adapt to changing cell dimensions while maintaining its function as a thermal barrier.

The source battery documentation specifically positions flexible PI foam as a way to combine thermal separation with compensation for cell expansion and assembly tolerances.

4.Electrical Insulation

Electrical insulation is another important requirement inside high-voltage battery systems.

Typical tested properties include:

Property	Typical Test Data
Volume Resistivity	10¹⁶–10¹⁷ Ω·cm
Dielectric Constant @ 1 MHz	2.8–3.2
Dielectric Loss @ 1 MHz	0.006–0.007
Dielectric Strength	1.8 kV/mm

This combination of thermal and electrical insulation allows PI foam to perform multiple functions within a battery pack.

Cell-to-Cell Thermal Barriers

One of the most promising applications for flexible polyimide foam is between adjacent lithium-ion cells.

Traditional cell-to-cell insulation may use materials such as:

Aerogel

Mica

Ceramic fiber materials

Silicone foam

Flame-retardant PU or EVA foam

Discuss Cell Insulation

Each material solves a different part of the problem.

Aerogel provides extremely low thermal conductivity but is relatively brittle and provides limited compression recovery.

Mica provides excellent high-temperature and electrical insulation but is rigid and cannot accommodate significant cell expansion.

Conventional polymer foams provide cushioning but generally offer lower high-temperature performance.

JLON PI foam is particularly useful when the design requires:

Thermal insulation + flame resistance + elasticity + electrical insulation

in the same component.

Polyimide Foam for EV Battery Packs

Electric vehicle battery packs require thermal protection while minimizing additional weight and occupied space.

JLON PI foam can be used in several locations within an EV battery pack.

Between Battery Cells

Flexible PI foam can act as a thermal barrier and compression layer between cells.

It helps accommodate cell swelling while maintaining separation between adjacent cells.

Battery Pack Bottom

PI foam can be used as a lightweight thermal and cushioning layer between battery modules and the lower enclosure.

Battery Pack Side Walls

Die-cut PI foam components can be installed between battery modules and pack side walls to provide insulation and mechanical cushioning.

Battery Pack Upper Cover

PI foam can be used beneath the upper cover where thermal insulation, electrical insulation or lightweight cushioning is required.

Module-to-Enclosure Interfaces

Custom-cut components can compensate for assembly tolerances while maintaining thermal separation between battery modules and surrounding structures.

Battery application documentation identifies pack bottoms, side areas and upper-cover linings as suitable PI foam locations where insulation, cushioning and fire-protection functions can be combined.

Discuss Your Battery Pack

Polyimide Foam for Energy Storage Systems (BESS)

Battery energy storage systems introduce another level of thermal protection beyond individual cells and battery packs.

JLON PI foam can be applied across several protection levels:

Cell → Module → Battery Pack → Energy Storage Cabinet

This allows one material platform to be considered for multiple thermal management locations within a BESS installation.

Cell & Module Level

PI foam can be installed between cells or modules to provide:

Thermal separation Expansion compensation

Mechanical cushioning Electrical insulation

Battery Pack Level

Inside an energy storage battery pack, PI foam may be used around:

Pack bottom Side walls Upper cover Module interfaces

The combination of resilience and insulation is particularly useful where rigid thermal barriers cannot accommodate component movement.

Energy Storage Cabinet Insulation

PI foam can also be integrated into energy storage cabinet doors and wall structures.

A typical construction may use:

Metal Panel + PI Foam Insulation + Metal Panel

Compared with traditional fibrous insulation, flexible PI foam offers several practical advantages:

Lightweight construction

No loose fibers

Easy die cutting

Custom shapes

Good moisture resistance

Thermal insulation

Flame-resistant characteristics

Simple assembly

It can therefore be considered for:

BESS cabinet doors

Battery compartment walls

Cabinet side panels

Internal thermal partitions

Pack-to-cabinet interfaces

The energy-storage source specifically describes cell-level, pack-level and cabinet-enclosure protection as three distinct PI foam application layers.

Typical Battery-Grade PI Foam Test Data

Test Item	Condition	Typical Result
Thermal Conductivity	23 ± 2°C	0.04 W/(m·K)
Thermal Barrier Test	650°C hot side	Max. cold side ≈172°C
Alternating Stress Test	5–15 MPa	7% stress loss
Compression Set	50% compression, 50°C × 168 h	<15%
Flame Resistance	GB/T 2408-2021	V-0 level
Volume Resistivity	Typical sample	10¹⁶–10¹⁷ Ω·cm
Dielectric Constant	1 MHz	2.8–3.2
Dielectric Loss	1 MHz	0.006–0.007
Dielectric Strength	Typical sample	1.8 kV/mm

Important: Values shown are representative test results and should not be treated as guaranteed values for every density, thickness or product configuration. Final material selection should be based on the required application and corresponding specification.

PI Foam vs Aerogel vs Mica vs Ceramicized Silicone

Selecting a battery thermal barrier depends on more than thermal conductivity alone.

Material	Thermal Insulation	Flexibility	Compression Recovery	High-Temperature Resistance	Electrical Insulation	Typical Advantage
Polyimide Foam	Very Good	Excellent	Excellent	Excellent	Excellent	Multi-functional thermal + cushioning layer
Aerogel	Excellent	Limited	Limited	Excellent	Good	Extremely low thermal conductivity
Mica	Moderate	Poor	Poor	Excellent	Excellent	Rigid high-temperature electrical insulation
Ceramicized Silicone	Good	Good	Good	Excellent	Good	Fire protection and sealing

When PI Foam Is Particularly Suitable

Polyimide foam is not intended to replace aerogel or mica in every battery design.

Its main advantage is functional integration.

Where a battery designer needs:

thermal insulation + compression + cushioning + electrical insulation

PI foam can reduce the need to combine several separate materials.

The underlying comparison data also identify PI foam's main distinction as its combination of elasticity, light weight and inherent flame resistance, while recognizing aerogel's stronger pure thermal-insulation performance.

Get Material Advice

PI Foam + Aerogel Composite Solutions

Some battery designs require both extremely low thermal conductivity and mechanical resilience.

In these applications, PI foam can also be combined with other thermal protection materials.For example:

Aerogel + PI Foam

The aerogel layer provides extremely low thermal conductivity, while PI foam provides compression recovery and mechanical support.

Mica + PI Foam

where rigid electrical and high-temperature protection is combined with a resilient cushioning layer.

Multi-layer thermal barrier structures are increasingly relevant as battery packs become more compact and cell-to-pack or cell-to-chassis architectures reduce available packaging space.

Flexible Processing for Battery Pack Integration

JLON PI foam can be converted according to battery pack drawings and assembly requirements.

Available processing options include:

Sheet supply

Custom thickness

Custom density

Die cutting

CNC cutting

Custom-shaped components

Adhesive-backed parts

Cell spacers

Battery pack liners

Pre-cut installation kits

Adhesive-backed configurations can simplify positioning during battery pack assembly.

The uploaded battery documentation specifically includes hot-pressed/die-cut parts and optional high-temperature adhesive-backed structures.

Why JLON Polyimide Foam?

JLON focuses on high-performance foam materials for demanding thermal management and insulation applications.

Rather than selecting a material based only on its maximum temperature rating, we recommend evaluating PI foam according to the complete battery operating condition, including thermal load, compression, available space and expected lifetime.

PI foam material selection

Flexible density and thickness options

Battery thermal barrier design support

Die-cut components

Adhesive-backed parts

Custom shapes

Thermal conductivity data

Compression test data

Flame-resistance test data

Electrical insulation data

Sample evaluation

Talk to Our Team

FAQ — Polyimide Foam for EV Battery & Energy Storage

What is a battery thermal barrier?

A battery thermal barrier is a passive insulation layer installed between cells, modules or other battery components to reduce heat transfer and help delay thermal runaway propagation.
Can polyimide foam be used between lithium-ion battery cells?

Yes. Flexible PI foam is particularly suitable where both thermal insulation and compression recovery are required.
It can help accommodate cell expansion and assembly tolerances while maintaining separation between adjacent cells.
Can polyimide foam prevent thermal runaway?

Polyimide foam should not be described as a material that independently “prevents” thermal runaway.
Its function is to act as part of a passive thermal protection system by reducing heat transfer and helping delay thermal propagation to neighboring components.
Final thermal runaway performance must be validated at cell, module, pack or system level.
Is polyimide foam suitable for EV batteries?

Yes. Typical applications include cell-to-cell thermal barriers, battery module insulation, pack liners and module-to-enclosure cushioning and insulation.
Its combination of low thermal conductivity, compression recovery and electrical insulation makes it particularly relevant to high-energy-density battery packs.
Can PI foam be used in BESS energy storage systems?

Yes.
PI foam can be used at cell, module, pack and cabinet level in battery energy storage systems.
Typical BESS applications include cell spacers, pack liners, cabinet door insulation and enclosure thermal barriers.
Is PI foam better than aerogel for battery insulation?

Neither material is universally better.
Aerogel generally provides lower thermal conductivity, while PI foam provides substantially better resilience and compression recovery.
PI foam is therefore particularly useful when a battery thermal barrier must provide both insulation and mechanical compliance.
Hybrid aerogel + PI foam structures may also be considered.
Is PI foam better than mica?

Mica provides excellent high-temperature and electrical insulation but is rigid.
PI foam is more suitable where flexibility, cushioning or cell expansion compensation is required.
The two materials can also be combined in multi-layer structures.
Can JLON supply die-cut battery insulation parts?

Yes.
PI foam can be supplied as sheets or converted into custom die-cut and CNC-cut components according to customer drawings.
Adhesive-backed parts are also available for easier assembly.
What information is required for a quotation?

Please provide the required thickness, density if specified, dimensions, application location, operating temperature, compression requirement, adhesive requirement and expected quantity.
For battery-cell applications, cell type and available spacing are also useful.